The present invention relates to an electrical system. More particularly, the present invention relates an electrical system for controlling electrically operable resources installed on a vehicular platform such as a recreational vehicle, conversion bus, or motor coach.
The conversion of a bus chassis or shell into a luxury recreational vehicle, corporate coach, or other customized motor coach involves hundreds of man-hours for the installation of numerous materials and components, specialized fabrications, hundreds of special purpose components, hundreds of feet of electrical wire, and so forth. Depending upon the extent of the conversion, the resulting coach may sell for as much as two million. Each of these highly customized coaches is typically made from a chassis or conversion shell which is built-up with the features and materials and in the configuration specified by the customer.
In terms of the converter's manufacturing operations, the conversion business is characterized by high complexity, low volume (i.e. a production/manufacturing lot size of one since each unit is unique), high rework (as customers routinely review the unit during its construction, typically making changes), and high feature content (incorporating the latest consumer features such as motor lifted plasma TV's, DVD players, and so forth). Each customer decides the particular layout of their coach. Customer decisions include placement of accent lighting in various parts of the coach, incorporation of slide out portions to increase interior space, selection of various appliances such as refrigerators and air conditioning systems, specification of various electronic devices such as rearward camera systems for increasing driver visibility, citizens band or other communications systems, security and alarm systems, and so on.
Each of the electrically operable features typically involves the placement of switches, one or more gage or display indicators, and wiring from multiple power sources such as chassis/engine and house batteries, shore power facilities, alternators, and generators. Existing electrical systems have typically involved point-to-point or discrete wiring for each electrical device, display, switch, and so forth. Such systems involve wire routings that are specific to the particular customer order, and the wiring often needs to be pulled through the walls, the chassis, and other difficult to reach areas throughout the coach. Accommodating customer change orders is usually labor intensive. The addition of a single feature typically requires rewiring control panels where the feature is controlled or monitored, pulling additional wires throughout the coach to connect the feature to various power sources, reworking fuse panels, circuit breakers, junction boxes, and other connection points to allow for the added feature. Adding a feature also requires updating numerous engineering drawings to document wire routings, revised system schematics, and so forth.
The automotive industry has developed multiplexing as a way to reduce the amount of wiring within a motor vehicle. In particular, a vehicle electrical system may incorporate networked intelligent nodes that communicate with a central control processor across a controller area network (CAN) bus. Instead of running discrete wires from, for example, multiple sensors, back to a central processor, each sensor is an intelligent node which communicates across multiple CAN bus back to a central processor. Each intelligent node requires a microprocessor for executing programming instructions and means to communicate on the CAN bus.
An example of a system using a central control processor is U.S. published patent application 2003/0105567, entitled “Mobile Energy Management System,” by Koenig, et al., which discloses a local area network (LAN) for managing the power provided to various electrical appliances installed in a recreational vehicle. The LAN consists of a master node for managing which appliances are to receive power depending upon a priority scheme for the appliances and the available power. Sensors are used to detect the type of external power source connected to the vehicle. Various appliances may be automatically shut down when the power supply cannot meet demand.
The recreational vehicle industry has considered using a fully distributed network architecture comprising intelligent nodes that communicate with each other on a peer-to-peer basis. An example is the LonWorks® system by Echelon Corporation of Palo Alto, Calif. Each device in the LonWorks® system is an intelligent node having a microprocessor and means for communicating on a network bus. Each device is able to communicate directly with every other device on the network. Consequently, each device hears all communications on the network bus. For example, a lighting device on the network will continually listen to all communications on the network bus until it recognizes a command that it can execute (e.g. turning on or off). Likewise, a switch device attempting to control the lighting device will listen until the network bus is available, transmit the controlling command, and listen for an acknowledgement from the lighting device. Alternatively, the switch device attempting to control the lighting device may repeatedly retransmit the controlling command until an acknowledgement is received from the lighting device.
Other systems have been developed to address various control aspects. For example, U.S. Pat. No. 4,262,212, entitled “Automatic Power Control Circuit for Recreational Vehicle or the like,” by Jacob, et al., provides a control circuit for automatically switching between vehicle power sources. When load requirements exceed the power available from one source, for example a land line (also called shore power), the generator is automatically started and the power source is switched to the generator.
U.S. Pat. No. 5,581,130, entitled “Circuit Board for the Control and/or Power Supply of Electrical Function Devices of a Vehicle,” by Boucheron, discloses a circuit board with removable modules for modifying vehicle circuits to accommodate various optional accessories in the vehicle. The circuit board aggregates wiring connections into a “cabin computer” where modules may be added or removed as needed.
U.S. Pat. No. 5,869,907, entitled “Modular Wiring Harness for a Vehicle,” by Marler, discloses a motorcycle wiring harness design with repositioned fuses, splices, relays, circuit breakers, and other in-line features to form a system module with diagnostic indicator lights intended to help simplify the aftermarket rebuilding or customization of motorcycles.
What is needed is an electrical system for controlling coach resources that provides improved reliability and economy.
The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.